Touch panel technology has advanced greatly over the past few years, from resistive touchscreen arrays capable of detecting a single touch coordinate, to capacitive touch panel systems capable of detecting multiple touch points on the touch panel, and decoding various swipes and gestures that may be used by application programs. For example, a right-handed swipe across the panel may be used by an application to change pages, while moving the tips of two fingers in opposite directions on the panel may be used by application to initiate a visual zoom of displayed media.
Touch panels have also advanced with respect to the form factor of the capacitive touch panel. For example, on-cell technology may be used to provide a thinner form factor by placing the capacitive touch panel on top of an LCD display panel with a small air gap between the capacitive sensor panel and the LCD display. More recently, in-cell technology has been developed in which the touch panel and the LCD display are integrated together, thereby making the display thinner, brighter, and less expensive compared to previous display technologies. As the physical dimensions of the touch panel and display shrink, however, the coupling between the LCD panel and the touch sensing signal becomes stronger, and switching noise generated by the LCD display may interfere with sensing functions of the touch panel. In some systems, sensing of the touch panel array may be performed during times in which signals driving the touch panel are not actively switching, such as during the horizontal or vertical display porch time.